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Calcium supplements with or without vitamin D and risk of cardiovascular events: reanalysis of the Women’s Health Initiative limited access dataset and meta-analysis

BMJ 2011; 342 doi: (Published 19 April 2011) Cite this as: BMJ 2011;342:d2040

Why would calcium supplements increase myocardial infarcts?

Magnesium and calcium compete for absorption, and high doses of
calcium possibly tip some of the 50% of people who have marginal magnesium
intake (1), into deficiency. Magnesium, as well as being important for
parathyroid hormone and therefore, bone density, is also nature's calcium
channel blocker. Low magnesium levels increase dangerous arrthymias (2)
increase hypertension (3), myocardial infarction and other adverse cardiac
effects (4).

For these reasons nutritional doctors use calcium and magnesium in a 2:1
ratio and we suspect that this prevents many problems. Evidence for this
is lacking and definitely needed. Comments to

1. Sebastian RS, Cleveland LE, Goldman JD, Moshfegh AJ. Older adults
who use vitamin/mineral supplements differ from nonusers in nutrient
intake adequacy and dietary attitudes. J Am Diet Assoc. 2007

2. Nielsen FH, Milne DB, Klevay LM, Gallagher S, Johnson L. Dietary
magnesium deficiency induces heart rhythm changes, impairs glucose
tolerance, and decreases serum cholesterol in post menopausal women. J Am
Coll Nutr. 2007 Apr;26(2):121-32.

3. Yogi A, Callera GE, Antunes TT, Tostes RC, Touyz RM. Vascular biology
of magnesium and its transporters in hypertension. Magnes Res. 2010

4. Shechter M. [Body magnesium--the spark of life].[Article in Hebrew]
Harefuah. 2011 Jan;150(1):41-5, 67.

Competing interests: No competing interests

26 July 2011
Margaret E Taylor
Nutritional GP
Adelaide, Australia